STCF01 Step-up Converter for Cell Phone Camera Flash LEDs Preliminary Data Features ■ Supply voltage range: 2.6V to 5.5V ■ 17V Maximum Output Voltage ■ Two levels of current up to 300mA set with external resistors ■ Dedicated pin to select the required level of current ■ Operating frequency: 1.5MHz: PWM Controller ■ Torch mode supported ■ Shutdown pin with true load disconnection ■ Efficiency: 90% at 100mA; 80% at 300mA ■ DFN10L (3mm x 3mm) Package DFN10L (3x3) to set the required current for each level. Compared to the linear current control technique, this method allows designers to achieve the best and most efficient performance possible with the selected current, thereby avoiding linear element losses. Description The STCF01 is a dedicated IC designed to drive two, three, or four white, cell phone camera flash LEDs with constant current. The step-up (boost) converter input is connected directly to the battery, and its converter output voltage is automatically determined using current feedback-based duty cycle control. The STCF01 has a dedicated pin for two levels of LED current selection. An external resistor is used The Shutdown (SHDN) pin saves power when the camera flash is not used by consuming less than 0.1µA of current. When the SHDN pin is high (logic '1'), the device is turned OFF and there is no DC current path from the supply to the white LEDs (Load Disconnect). If it is held to GND, the output current continuously flows through the LEDs (Torch mode). The SHDN pin, when it is set to low (logic '0'), is also used to set the flash function time duration. Order Codes Type Package Comments STCF01PMR DFN10L (3mm x 3mm) 4500 parts per reel October 2005 This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice. Rev. 1 1/16 www.st.com 16 STCF01 Contents 1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Application Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Electrical Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7 Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8 Package Mechanical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2/16 STCF01 1 Figure 1. 1 Diagram Diagram Block Diagram 3/16 STCF01 2 Pin Configuration 2 Pin Configuration Figure 2. Pin Connnections (Top View ) Table 1. Pin Description PlN N° SYMBOL 1 PWRGND 2 OVP 3 VI 4 HC 5 LC 6 SGLGND 7 FB 8 SEL 9 SHDN 10 SW 4/16 NOTE This is the application power signal reference. Connect the input and output capacitors to this pin. This pin senses step-up output voltage, which provides overvoltage protection in the event that the output voltage exceeds the OVP threshold This pin supplies the input voltage for the step-up stage as well as the supply voltage for the overall device. This pin sets the high level current for the white LEDs with a resistor that is connected between this pin and VI. This pin sets the low level current for the white LEDs with a resistor that is connected between this pin and VI. This pin is the logic signal reference for the IC. This pin senses the current flowing through the white LEDs and uses this feedback to provide current regulation. This pin is used to select the signal level of the white LEDs; a low level signal sets the low level LED current, while the high level signal sets the high level LED current. This pin enables or disables the Shutdown mode. A high level signal enables device Shutdown mode, where most of the device internal logic is turned OFF. If this pin is held to GND, the output current flows through the LEDs continuously (Torch mode). This is the switch node pin, which is connected to the internal N-channel MOSFET drain. STCF01 3 Figure 3. 3 Application Information Application Information Application Circuit 5/16 STCF01 4 Maximum Ratings 4 Maximum Ratings Table 2. Absolute Maximum Ratings Symbol Parameter VI VSW FB, SEL, SHDN, LC, HC OVP ESD PTOT TOP TJ TSTG Note: Table 3. Symbol Value Unit DC Input Voltage to SGLGND -0.3 to 6 V Switch Voltage -0.3 to 20 V Voltage Range -0.3 to VI + 0.3 V -0.3 to 20 ±2 1.5 V kV mW Over Voltage Protection Human Body Model Continuous Power Dissipation (at TA = 70°C) Operating Junction Temperature Range -40 to 85 °C Junction Temperature -40 to 125 °C Storage Temperature Range -65 to 150 °C Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional Operation under these conditions is not implied. Thermal Data Parameter Value Unit RthJA Thermal Resistance Junction-Ambient 30.9 °C/W RthJC Thermal Resistance Junction-Case 2.96 °C/W 6/16 STCF01 5 5 Electrical Characteristics Electrical Characteristics Table 4. DC Electrical Characteristics (TJ = -40°C to 85°C, VI = 3.6V, CI = 2.2µF, CO = 4.7µF, L = 10µH, RLC = 12kΩ, RHC = 4kΩ, VOVP = 8V, Typ. values @ 25°C, unless otherwise specified) Symbol Parameter Test Conditions Min. Typ. Max. Unit 5.5 V General Section VI VUVLO IQ fSW Max Operation Supply Voltage Under Voltage lockout threshold Quiescent Current Switching Frequency VOVP Over Voltage Threshold IPKMax Maximum Inductor Current VSEL= 0V, VSHDN = 0V, Min. duty cycle VSEL= 0V Shutdown Mode VSEL= 0V, VSHDN = 0V No Load VSHDN = 0V 2.3 2.45 2.6 V 1.2 2.3 0.1 1.5 3 0.5 1.8 mA µA MHz 17 18 19 V 1.2 A Current Control VHC HC Pin Voltage VSEL= 3V, VSHDN = 0V VI-0.65 VI-0.6 VI-0.55 V VLC LC Pin Voltage VSEL= 0V, VSHDN = 0V VI-0.65 VI-0.6 VI-0.55 V ILED/IHC High Level Current Multiplier VSEL= 3V, VSHDN = 0V (25°C) 1900 2100 2300 A/A ILED/ILC Low Level Current Multiplier VSEL= 0V, VSHDN = 0V (25°C) 2200 2400 2600 A/A Resistance ON Feedback IFB = 100mA 1.2 Current Feedback Leakage VSHDN = 3V, VFB = VI 0.1 1 µA ISW = 1A Note: 1 0.3 RONFB IFB(LEAK) Ω Switch Section RON Internal Switch ON-Resistance ISW(LEAK) Internal Switch Leakage Current VSHDN = 3V, VSW= 16.5V DMAX IFB = 0mA Maximum Duty Cycle DMIN Minimum Duty Cycle 0.1 IFB = 200mA; VSEL = 0V Pulse Skipping Ω 1 µA 90 % 0 % Control Input Section VH(SEL) SEL and SHDN Input High VH(SHDN) Threshold VL(SEL) VL(SHDN) SEL and SHDN Input Low Threshold VI = 2.6V 1.2 VI = 3.6V 1.4 VI = 5.5V 1.6 V VI = 2.6V 0.4 VI = 3.6V 0.5 VI = 5.5V 0.6 V Thermal Shutdown TSD Thermal Shutdown 145 °C THS Thermal Shutdown Hysteresis 15 °C Note: 1 Typical value, not production tested 7/16 6 Detailed Description 6 STCF01 Detailed Description The STCF01 white Led boost converter drives two up to four white LEDs with a constant current. It needs few external components: two ceramic capacitors (CI=2.2µF CO=4.7µF), one inductor L=10µH and one schottky diode. The device works with a minimum VI=2.6V, and it has an Over Voltage Protection on the output guaranteed at minimum value equal to 17V. This value ensures proper operation with a maximum of four White LEDs in series. In the worst case of VI=2.6V at VOVP=8V (typical value of two LEDs) it is possible to obtain IO=270mA, while at VOVP=11V (typical value of three LEDs) it is possible obtain IO=180mA (Figure 4: Maximum Output Current Vs Input Voltage). The maximum IO current is limited by inductor peak current internally set at Typ 1.2A. This feature allows saving the battery life from intensive use of the flash. The SEL pin allows to select high and low current value flowing on the White LEDs. The two current values are set through external resistors RHC and RLC according the following formula: ILED(FLASH) = 2100 * (VI - VHC) / RHC ILED(TORCH) = 2400 * (VI - VLC) / RLC An High logic level on SHDN pin puts the device in shutdown mode; if it is hold to Low the flash or torch mode is activated. When the SHDN pin is LOW the device provides the requested current in less than 200µs (see TURN ON TIME plot). This fast turn-on time makes the device suitable for single shoot and multiple shoot operation modes. 8/16 STCF01 7 7 Typical Operating Characteristics Typical Operating Characteristics (TJ = -40°C to 85°C, VI = 3.6V, CI = 2.2µF, CO = 4.7µF, L = 10µH, RLC = 12kΩ, RHC = 4kΩ, VOVP = 8V, Typ. values @ 25°C, unless otherwise specified). Figure 4. Maximum Output Current Vs Input Voltage Figure 5. Maximum Output Current Vs Input Voltage Figure 6. Efficiency Vs Temperature Figure 7. Efficiency Vs Temperature Figure 8. Efficiency vs Temperature Figure 9. Quiescent Current at Full Operation Vs Temperature 9/16 STCF01 7 Typical Operating Characteristics Figure 10. Feedback Voltage Vs Temperature Figure 11. Current Feedback Leakage Vs Temperature Figure 12. VI-VLC Vs Temperature Figure 13. VI-VHC Vs Temperature Figure 14. Peak Inductor Current Vs Temperature Figure 15. RONFB Vs Temperature 10/16 STCF01 Figure 16. Maximum Duty Cycle Vs Temperature 7 Typical Operating Characteristics Figure 17. Turn On and Off Response VSHDN=pulse, FREQ.=1Hz, Tr=Tf=10µs Figure 18. Turn On Time Figure 19. Start Up Transient VSHDN=pulse, FREQ.=1Hz, Tr=Tf=10µs VI=0 to 3.6V, VSEL=GND, VSHDN=GND Figure 20. Multi Shoot Mode Figure 21. Torch Mode Behavior VSEL=GND, VSHDN=pulse VSEL=GND, VSHDN=GND 11/16 8 Package Mechanical Data 8 STCF01 Package Mechanical Data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect. The category of second Level Interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com. 12/16 STCF01 8 Package Mechanical Data DFN10 (3x3) MECHANICAL DATA mm. mils DIM. MIN. TYP MAX. MIN. TYP. MAX. 0.80 0.90 1.00 31.5 35.4 39.4 A1 0.02 0.05 0.8 2.0 A2 0.70 25.6 A3 0.20 7.9 A b 0.18 D D2 2.21 7.1 2.26 1.29 1.34 2.31 87.0 0.55 11.8 89.0 91.0 118.1 1.39 50.8 0.50 0.45 9.1 118.1 3.00 e L 0.30 3.00 E E2 0.23 52.8 54.8 19.7 0.65 17.7 21.7 25.6 7426335A 13/16 STCF01 8 Package Mechanical Data Tape & Reel QFNxx/DFNxx (3x3) MECHANICAL DATA mm. inch DIM. MIN. TYP A MIN. TYP. 330 13.2 MAX. 12.992 C 12.8 D 20.2 0.795 N 60 2.362 T 14/16 MAX. 0.504 0.519 18.4 0.724 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.315 STCF01 9 9 Revision History Revision History Date Revision 10-Oct-2005 1 Description of Change First Release. 15/16 STCF01 9 Revision History Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. 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